Conventionally, for ensuring the confidentiality of information such as secret information, various approaches to security have been proposed. For example, secret information is encrypted, and the encrypted secret information is managed with the addition of authentication information such as password thereto. When the browse and use of the secret information is needed, user authentication is performed by a predetermined authentication method using a password or the like. When this authentication confirms user's validity, the encrypted secret information is decrypted to permit the browse and use of the secret information. In such a manner, user authentication of secret information is performed through authentication information such as password to protect secret information against leakage of secret information, tampering of secret information, interference with use of secret information, and other risks, thereby strictly managing secret information.
In recent years, there has been a tendency to the emphasis on security to digital multifunction devices used by a unspecified number of users, such as digital multifunction devices with such functions as copy, fax, printer, and scanner, which are installed in offices and other places. That is, when data processing such as image processing is performed with a digital multifunction device, data are protected against data leakage and data tampering, and other risks, thereby strictly managing secret information. More specifically, as in the case of the above secret information, data is encrypted, and authentication information is added to the encrypted data. When data processing for the data is requested to the digital multifunction device, user authentication is performed in accordance with the authentication information added to the data. When this authentication confirms the identity of a user, the encrypted data are decrypted to permit a predetermined data processing with the digital multifunction device.
One example of such a digital multifunction device with a security system is a printing device disclosed in Japanese Laid-Open Patent Application No. 28850/1999 (Tokukaihei 11-28850; published on Feb. 2, 1999). The printing device disclosed in Japanese Laid-Open Patent Application No. 28850/1999 is arranged so that printing of a confidential document and a private document is carried out after receiver authentication for the confidential document and the private document is performed through receiver's input of an ID and a password as authentication information.
Moreover, Japanese Laid-Open Patent Application No. 293036/1997 (Tokukaihei 9-293036; published on Nov. 11, 1997; counterpart U.S. Pat. No. 6,163,383 (issued on Dec. 19, 2000)) discloses a printing device that performs user authentication in accordance with authentication condition, which are attached previously to data to be printed, for authenticating a user of the printing device. In this printing device, the authentication condition attached to the data includes authentication levels set in accordance with desired security levels such as level of data importance. Therefore, user authentication based on the authentication condition is performed in accordance with the set authentication levels, and the user authentication is performed strictly or leniently in accordance with the security levels.
Further, Japanese Laid-Open Patent Application No. 2001-306173 (Tokukai 2001-306173; published on Nov. 2, 2001) discloses an information processor that performs user authentication with authentication levels changed in accordance with an amount of power consumption and an installation location of the information processor. Specifically, the authentication levels are changed by changing complexity of a password inputted when user authentication is performed. That is, the information processor performs user authentication by automatically changing the password in accordance with the possibility of unauthorized use by a third party in such a manner that a complex password is used in a situation in which there is a high possibility of unauthorized use, and an easy password is used in a situation in which there is a low possibility of unauthorized use. This makes it possible to change a security level in accordance with an environment in which the information processor is used.
As described above, digital multifunction devices and information processors with various security systems have been proposed.
However, the conventional printing devices have the problem that slowdowns of data processing such as image processing may be caused in the printing devices due to too much emphasis on the security aspect. That is, in the conventional printing device, regardless of the volume of data processing in the print processing device, consideration is given to ensuring of security including the protection against data leakage, data tampering, and other risks. On this account, even when the large volume of data processing rushes to the print processing device, user authentication is performed at a predetermined authentication level which is set in accordance with importance of data. As a result, it takes much time to authenticate users, thus causing slowdowns of data processing in the printing device.
Furthermore, this problem would also occur when the security system carried out in the information processor disclosed in Japanese Laid-Open Patent Application No. 2001-306173 is applied to a printing device. That is, in the case where the security system of Japanese Laid-Open Patent Application No. 2001-306173 is applied to a printing device, the user authentication level changes in accordance with the possibility of unauthorized use of data in the printing device, not the volume of data processing in the printing device. In other words, the user authentication level does not change in accordance with the volume of data processing requested to the printing device. Therefore, in the case where the large volume of data processing is required to handle, it takes much time to authenticate users. This might cause slowdowns of data processing in the printing device.
Besides, unlike the information processor disclosed in Japanese Laid-Open Patent Application No. 2001-306173, a printing device is installed at a predetermined location and used by an unspecified number of users. On this account, it is difficult to determine the possibility of unauthorized use by a third party and change an authentication level in accordance with power consumption and installation location of the printing device.
Thus, the conventional printing devices do not change a user authentication level in accordance with the volume of data processing requested to the printing devices. In other words, in the conventional printing devices, regardless of the volume of data processing in the print processing devices, data security is ensured only in accordance with level of data importance. Therefore, a requested large amount of data processing might cause a decrease in processing power of the printing device. Further, such a decrease in processing power of the printing device results in reduction in the commercial value of the printing device.